firewire: add CSR CYCLE_TIME write support

The specification requires that CYCLE_TIME is writable so that it can be
initialized, so we better implement it.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

drivers/firewire/core-transaction.c

@@ -1097,6 +1097,9 @@ static void handle_registers(struct fw_card *card, struct fw_request *request,
 		if (TCODE_IS_READ_REQUEST(tcode) && length == 4)
 			*data = cpu_to_be32(card->driver->
 					read_csr_reg(card, CSR_CYCLE_TIME));
+		else if (tcode == TCODE_WRITE_QUADLET_REQUEST)
+			card->driver->write_csr_reg(card, CSR_CYCLE_TIME,
+						    be32_to_cpu(*data));
 		else
 			rcode = RCODE_TYPE_ERROR;
 		break;

drivers/firewire/ohci.c

@@ -1996,6 +1996,13 @@ static void ohci_write_csr_reg(struct fw_card *card, int csr_offset, u32 value)
 		flush_writes(ohci);
 		break;
 
+	case CSR_CYCLE_TIME:
+		reg_write(ohci, OHCI1394_IsochronousCycleTimer, value);
+		reg_write(ohci, OHCI1394_IntEventSet,
+			  OHCI1394_cycleInconsistent);
+		flush_writes(ohci);
+		break;
+
 	default:
 		WARN_ON(1);
 		break;